Variable pitch propeller



June 26, 1945. w 5, HOOVER 2,379,302

' VARIABLE PITCH PRDPELLER Filed May 6, 1941 3 Sheets-Sheet l h 3% Wail l4 /5 6' a /9 .30 4

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W. S. HOOVER VARIABLE PITCH PROPELLER Filed May 6, 1941 3 Sheets-Sheet 2 I J waJ \E;

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June 26, 1945. w. s. HOOVER VARTABLE PITCH PROIEIJLER Filed May 6, 1941 3 Sheets-Sheet 3 INVENTOR.

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E, Patented June 26, 1945 UNITED STATES PATENT OFFICE VARIABLE PITCH PBOPELLEB- Walter 8. Hoover, Montreal, Quebec, Canada Application May 6, 1941, Serial No. 392,019

Claims.

v limit stop in one position of the pitch adjusting range, and actuating means for adjusting the pitch setting to any desired position from the fixed position through an adjustable angle of approximately 20.

The invention is especially applicable for use in moderate sized engines such as 300 horsepower and is designed to be hand-controlled. although it is adapted to governor speed control if desired.

Another object of the invention is the provision of an integral hub design adapted for use interchangeably with both all-metal and wooden blade propellers.

Another object of the invention is the provision of a hydraulic actuator for the pitch setting mechanism which utilizes high pressure 011 supplied by a booster pump for advance pitch setting, while employing the lower pressure of the engine lubricating oil plus the blades centrifugal twisting moments for the low pitch setting.

The invention will become more apparent from a consideration of the accompanying drawings constituting a part hereof in which like reference characters designate like parts and in which:

Fig. l is a cross-sectional view through a propeller hub partially in elevation taken along the line l--l, Fig. 2;

Fig. 2 a front elevatlonal view partially in crosssection taken along the line 2-2, Fig. 1:

Fig. 3 a cross-sectional view through the hydraulic actuator housing taken along the line 3-4. Fig. 1;

Fig. 4 a top plan view of a booster pump and control valve;

Fig. 5 a cross-section taken along the line 5-5. Fig. 4;

Fig. 6 a cross-section taken along the line 6-5, Fig. 4;

Fig. 7 a cross-sectional view partially in elevatlon taken along the line 1-1, Fig. 4; and

Fig. 8 a cross-section of a portion of the hub structure with the propeller blade root in elevation.

With reference to Fig. l of the drawings, the structure therein illustrated comprises blades I of plastic and wood threaded on steel sleeves 2 by grooves 211 and threads 2b to provide bearing surfaces. Threaded onto the inboard end of these sleeves 2 are bevel gears 3 which are locked thereto with pins 4. A shoulder So on each gear 3 carries the blades centrifugal loads to a matched set .of stacked bearings consisting of three thrust bearings 5 and a reversed preloaded bearing 6. Blade retaining nuts I transfer these loads to the hub barrels l and support chevron-type oil seals 9 and assembly balancing rings II). A lock it is splined to the blade retaining nut I and attached to the hub barrel end by two small screws [2. A small pin I3 is fixed to this look H to lock the balancing ring l0. The blade retention nut I thus preloads the antifriction bearings I5 and i to evenly divide the load between them.

Meshing with the bevel gear 3 on the blade shank is a bevel gear H located and fixed in the hub concentric to the crankshaft b means of a ball bearing and a threaded ring l8 which screws into the hub barrel 8 and serves to preload the bevel gears 3 and it which take the centrifugal loading of the blades. A section'of the head of a screw lLwhich threads into the hub barrel 8, is engaged with an arc Ila On the periphery of this pre-load ring l6 to serve as a lock. Externally splined to the forward end of the bevel gear huh I! is a rin it which is internally splined to the shaft of a rotor l9. This adjusting ring it, which also serves to facilitate assembly, is held on the end of the shaft of rotor ID by a. split snap ring 20.

The rotor I9 is housed in a cylindrical dome 2| and is positioned and held therein by brass oil seal bushings 22 and 23 in such manner that it is free to rotate relative to the dome 2|. The rear bushing is pressed into a. torque plate 24 which is attached to the dome 21 by screws 25 and dowels 26. Torque plate 24 has serrations 240. that coact with serrations on hub barrel I whereby together with the external spline connections between ring l8 and bevel gear ll and the internal spline connection between ring it and rotor l9 angular adjustments in increments of .25 degree between rotor I9 and the blades may be made. A gasket 21 is interposed between the torque plate 24 and dome 2| so that an oil-tight chamber in which the rotor l 9 is sealed is formed. Also assembled in this chamber are abutments 28 which are fixed in place by two sets of dowels 29 and 30 set into the dome 2i and torque plate 2|, respectively. Micarta or other flexible oil seal strips 3| are placed between the abutments 28 and the rotor shaft l5.

Splined as shown at 19c onto the forward end of the rotor I9 is a metal ring 32, Fig. 3, having four lugs 32a which project between four corresponding lugs 33 on an encircling ring 33a that 2 asvasoa isexternallysplinedatilbtothedomcll. These rings 32 and 88 form the low angle limiting stops. A split snap ring ll holds the inner stop ring 32 on the rotor shaft is. .A circular plate II is held to the dome 2| by safety screws I8 and serves to retain the outer stop ring II. Inserted between this plate 35 and the dome 21 is a gasket 31 to seal the fluid in the rotor l9. Riveted to the plate SI is a Dzus fastener spring SI which engages with a mus fastener pin 39 to secure a spherical cap III to the dome 2 I.

The dome and rotor assembly mounts onto the front section of the hub barrel 8 concentric with the crank shaft 4| and is held thereon by a sectorshaped washer l2 and a nut 43 which encircles the dome 2| and threads into a cylindrical flange integral with the hub 8. Small screws ll lock this nut to the hub. As hereinbefore stated torque plate 24 is serrated to the hub barrel 8 to prevent the dome assembly from rotating and allow adjustment between rotor and dome, as well as to facilitate assembly.

The propeller is centered on the crankshaft 4| by conventional front and rear cones Ila and lb, respectively, the latter being secured thereon by a retaining nut 45. A chevron type oil seal 46 is compressed between this nut 45 and the cone lib to stop seepage of oil into the splines. The nut 45 is locked by a clevis pin 11 which is kept in place by an oil distributor tube It inside the crankshaft. This tube is located on the inside taper of the shaft ll and is held in place by a nut 49 threaded into the cone retaining nut 45 and locked thereto with safety wire.

This tube 48 projects beyond the front of the hub barrel 8 so that the dome and rotor fits over it in such a manner that two annular grooves which connect with two separate oil channel a and b formed in the tube lll are, respectively, adjacent to forward and rear sets of holes drilled respectively from the opposite sides of the rotor vanes to the rotor bore. Thus oil in the forward channel a is led out to one side of the rotor vanes and oil in the rear channel b to the opposite side. Carried in grooves along the top face in each rotor vane are fibrous oil seals 50 which are pressed against the dome wall by oil pressure in a small hole c running from the grooves to the holes matching with the forward all channel 0. Metallic oil seal rings ii are placed between the rotor bore and the oil distributor tube I! to minimize leakage.

Oil under engine'pressure is supplied to the rear channel I; and reaches the hub for lubricating purposes through a small radial hole e, and the rotor 19 is pressure balanced by the engine pressure oil through gland e.

Oil under high pressure is supplied to the forward channel a of the distributor tube 48 by the gear type booster pump generally designated by the numeral 52, Figs. 4, 5, 6 and T. This booster pump 52 is mounted onto a pump pad by means of studs through the base 53. Engine oil is admitted into the inlet pump chamber through a hole d tapped into the base 53.

Immediately adjacent the pump chamber are a pair of pump gears 54 and 55. One of these gears, 54, the driver, is formed integral with a drive shaft 58 which is located by two oil seal bushings 59 and 60 shrunk into the pump base 83 and the pump cap SI, respectively. The driven gear I! encircles a brass bearing 56 seated in receases in the base 58 and cap 81.

A manually controlled valve 82 is seated in a bushing l8 shrunk in the cap 51. A sleeve 64 fixed to the cap by two screws ll serves to guide and hold this valve 62 in place. A ring of ball bearings N is interposed between the valve 82 and sleeve 64 to minimize friction. To limit oil leakage, a air of oil seals 81 are fitted around the valve stem and are held in place on top of the sleeve N by a nut 60 threaded onto it. A control lever 68 is attached to the valve stem by a taper pin 10 locked with safety wire Ilia. Formed integral with the lever 89 are two lugs 69a which limit the lever movement to 90 degrees by striking against the screws 65 holding the sleeve Bl. This lever 69 is provided with a hole 68b for attaching a contro1 rod or cable operated by the pilot.

After passing through the gear pump, the oil is pumped to a channel I leading to either the manual valve 62 or a relief valve 6|. When the lever 68 is in one position, high pressure oil is routed into the forward channel a of the distributor tube, Fig. l, and thence, through the matching holes a in the rotor vanes, into the chambers formed in the dome by the vanes and abutments 21. The pressure then exerted turns the rotor in the direction that causes the gear train to drive the blades to high pitch. The pressure against the abutments 21 is transmitted to the torque plate It partly by way of the dome and forward set of dowels 29 and partly directly by the rear set of dowels III. This torque is then transmitted to the hub barrel l by the splines of the torque plate ll.

when the control lever 89 is placed in the other position, the high pressure oil from the gear pump is blocked by the valve 62 and is diverted in a channel a leading to the relief valve 6|. This valve is locked by a helical spring H which is adjustable in compression by a long screw 12 threaded into the cap 51. A nut 13 is threaded onto screw 12 and locked thereto by a snap-ring H. The high pressure oil opens the relief valve BI and by-passes through a diagonal channel h back to the inlet chamber, from where the cycle is repeated until the valve 62 is changed. With the high pressure fluid thus being by-passed, a port 11 in the valve 62 connects the forward channel a of the distributor tube 18 to drain through openings K in the drive gear shaft 58, thus permitting engine oil pressure and the centrifugal twisting movements to turn the blades to low pitch.

In Fig. 8 is shown a modification of the propeller blade mounting of Fig. 1 which is adapted for the use of aluminum alloy blade propellers, the blade assembly being interchangeable with the plastic or wood type of blades illustrated in Fig. l of the drawings.

In Fig. 8 the aluminum alloy blade shanks are encased in split steel ferrules 8! which are held on to the blades bythe matched set of bearings 82. They are prevented from turning on the blades by cap screws 83 threaded under the blade roots. The outer extremities of the ferrules BI have a short length taper for receiving a one-piece nut 84 having a matching taper. This nut 84 threads to the ferrule and by pulling it up tightly, the ferrule is made to clamp the blade rigidly and thus restrain a movement of the blade relative to the ferrule III. A small screw 85 serves to lock the nut to the ferrule and in turn is held in place by the inner race of the outermost bearing.

To prevent the loss of hub lubricants, the outer extremity of the ferrule clamp nut 84 is provided with a chevron-type oil seal packing II, which is held in place by a split snap-ring ll expanding into a matching groove in the end of the nut 84.

The relief valve 6 I Fig. 5, is set somewhat above the engine oil pressure, plus the centrifugal twistforward end of the hub, a dome-shaped housing ing moments. Thus, to increase the pitch setting mounted in and secured to said axial flange, said of the blades, the high pressure oil is routed into housing being sealed from said propeller hub, a

eii'ect a low pitch setting of the blades: that is eating with the opposite sides of said rotor vanes to say, the hydraulic actuator assumes the fixed H stop position for the blades. means operable in one position to establish com- The hydraulic actuator with pilot control for munication oi the high pressure fluid source with high pitch setting only disclosed herein is espethe rotor vanes. and in another position to discially adapted for small places, and particularly connect the high pressure source of fluid and open for trainingpilots. m the high pressure fluid flow channel'to a drain It is designed to be rugged in construction and while simultaneously connecting the opposite to be immune from abuse through improper use. sides of the rotor vanes to the engine lubricating will be evident to those skilled in the art that pendently of the rotor vanes and stationary abutof construction without departing from the prin- 4. In a variable pitch propeller mechanism. a, ciples herein set forth." hub structure having angularly-spaced blade I claim: sockets for mounting propeller blades for rotary 1. In a variable pitch propeller mechanism, a movement therein, a blade-adjusting rotor geared hollow hub structure mounted for rotation with to the blades for simultaneously actuating the subjected to rotary movement for angular adpressure fluid on opposite sides of the vanes, said spouse to movement oi the rotor, and a torque rings constituting flxed limit stops to determine gether with the spline disk the rotor may be an- 5. In a variable pitch propeller mechanism, an

blades. rotary movement in said sockets. said blades hav- 2. In a variable pitch propeller mechanism, a ing gear teeth coacting with the teeth of amaster hollou hub structure mounted for rotation with gear and said hub having a flange extending teeth of an actuator gear to be simultaneously external periphery thereof enacting with comsubjected to rotary movement for angular adiustplementary shaped apertures in said hub flange, a

said rotor and external spline connection with the gear having serrations on the internal and exactuator gear to rotate the latter in response to temal periphery thereof coacting with complemovement of the rotor, a dome housing for said mentary shaped serrations in said rotor and masthe low angle limiting stops oi the propeller housing which together with the peripheral ser- 3. In a variable pitch propeller mechanism, a connecting ring being adjustable to obtain infinite hub structure having. a plurality of blade sockets adjustment of the rotor and propeller blade angle. for mounting propeller blades for rotary movement therein and having an axial flange at the 05 WALTER B. HOOVER. 

